1. Field of the Invention
The present invention relates to a thin film magnetic head in which a recording head (inductive magnetic head) and a reproducing head (magnetoresistive head) are combined, and more particularly, to a thin film magnetic head in which the tip and the vicinity thereof of an upper core layer can be formed in a predetermined shape, enabling the track to be narrowed, and to a method of fabricating the same.
2. Description of the Related Art
FIG. 11 is a longitudinal sectional view of a conventional thin film magnetic head.
The thin film magnetic head is provided on the trailing end of a slider of a floating type magnetic head which faces a recording medium such as a hard disk, and is a combined thin film magnetic head in which a magnetoresistive head for reproducing, using magnetoresistance, and an inductive magnetic head for recording, are laminated.
A lower shielding layer 1 is composed of a magnetic material such as an NiFe alloy (permalloy), and a magnetoresistive element layer 2 is formed on the lower shielding layer 1 with a first gap layer (not shown in the drawing) therebetween. An upper shielding layer 3, which is composed of a magnetic material such as an NiFe alloy, is formed on the magnetoresistive element layer 2. As described above, the thin film magnetic head shown in FIG. 11 is a combined thin film magnetic head in which a magnetoresistive head and an inductive magnetic head are laminated, and the upper shielding layer 3 also functions as a lower core layer of the inductive magnetic head. Hereinafter, the layer represented by numeral 3 is referred to as a lower core layer.
A gap layer 4 (second gap layer) composed of a nonmagnetic material such as aluminum oxide (Al.sub.2 O.sub.3) or silicon dioxide (SiO.sub.2) is formed on the lower core layer 3. An insulating layer 5 (first insulating layer) composed of a resist or other organic material is formed on the gap layer 4.
A coil layer 6, composed of a conductive material having low electrical resistance, such as Cu, is spirally formed on the insulating layer 5. Although the coil layer 6 is formed so as to go around a base 8b of an upper core layer 8, which will be described later, only a portion of the coil layer 6 is shown in FIG. 11.
The coil layer 6 is covered by an insulating layer 7 (second insulating layer) composed of an organic material or the like, and the upper core layer 8 is formed on the insulating layer 7 by plating a magnetic material such as a permalloy. The tip 8a of the upper core layer 8 is joined to the lower core layer 3 with the gap layer 4 therebetween at the section facing a recording medium to form a magnetic gap having a gap length Gl. The base 8b of the upper core layer 8 is magnetically connected to the lower core layer 3 through a hole made in the gap layer 4.
In the inductive magnetic head for writing, when a recording current is applied to the coil layer 6, a recording magnetic field is induced in the lower core layer 3 and the upper core layer 8, and a magnetic signal is recorded onto a recording medium such as a hard disk by means of a leakage magnetic field from the magnetic gap between the lower core layer 3 and the tip 8a of the upper core layer 8.
In the thin film magnetic head shown in FIG. 11, the coil layer 6 has a double-layered structure. The double-layered structure is employed for the purposes of enhancing writing efficiency by shortening the magnetic path formed over the lower core layer 3 and the upper core layer 8, and reducing inductance.
FIG. 12 is a longitudinal sectional view which shows a step of fabricating the upper core layer 8 of the thin film magnetic head shown in FIG. 11.
The upper core layer 8 of the thin film magnetic head shown in FIG. 11 is formed by frame plating. As shown in FIG. 12, after the coil layer 6 is formed and is covered by the insulating layer 7, an underlying layer 9 composed of a magnetic material such as an NiFe alloy is formed from on the gap layer 4, which is exposed around the tip, to on the insulating layer 7.
Next, after a resist layer 10 is formed on the underlying layer 9, a pattern of the upper core layer 8 is formed on the resist layer 10 by exposure and development, and a magnetic material layer (upper core layer 8) is formed by plating on the section in which the resist 10 is removed and the underlying layer 9 is exposed. When the remaining resist layer 10 is removed, the upper core layer 8 is completed. In the final step, by removing the thin film laminate on the left side of the line A--A (shown by dotted lines in the drawing), the thin film magnetic head having the shape shown in FIG. 11 can be obtained.
However, in the structure of the conventional thin film magnetic head as shown in FIG. 11, when the upper core layer 8 is formed by frame plating, narrowing of the track cannot be realized.
As shown in FIG. 11, by forming the coil layer 6 having a double-layered structure, the total thickness of the insulating layers 5 and 7 which cover the coil layer 6 is increased, and in such a state, as shown in FIG. 12, when the resist layer 10 is formed from on the gap layer 4 around the tip in which the insulating layers 5 and 7 are not formed to on the insulating layer 7, the thickness t1 of the resist layer 10 formed on the gap layer 4 is significantly increased. On the gap layer 4, as shown in FIG. 11, the tip 8a of the upper core layer 8 is formed. The tip 8a is narrowly shaped as shown in the plan view of FIG. 13, and the width of the tip 8a determines a track width Tw. In particular, as recording density is increased, the track width Tw must be further decreased, and the pattern of the resist layer 10 must be formed with particular precision when the tip 8a and its vicinity of the upper core layer 8 are formed.
However, as shown in FIG. 12, since the thickness t1 of the resist layer 10 on the gap layer 4, in which the tip 8a of the upper core layer 8 is to be formed, is significantly increased, when the wavelength of a light source for exposure is decreased and the depth of focus is increased, resolution (resolving power) is degraded and the track width Tw having a predetermined size cannot be obtained; it is thus not possible to meet the need for narrowing of a gap. In order to improve resolution, a smaller depth of focus is better.
Another reason for not being able to realize narrowing of the track is that since the thickness t1 of the resist layer 10 formed on the gap layer 4 differs greatly from that of the resist layer 10 formed on the insulating layer 7, irregular reflection may occur during exposure and development because of differences in focus.
FIG. 14 is a longitudinal sectional view of another conventional thin film magnetic head.
In FIG. 14, a lower shielding layer 11 is partially formed only around the tip, and a magnetoresistive element layer 12 is formed on the lower shielding layer 11. A lower core layer 13 (upper shielding layer) is formed from on the magnetoresistive element layer 12 and to in the rear of the lower shielding layer 11. A coil layer 14 is formed on the lower core layer 13, and an upper core layer 15 is formed so as to face the lower core layer 13 at the tip and to extend over an insulating layer 17 formed on the coil layer 14.
In the conventional example, the lower shielding layer 11 is partially formed only around the tip, and in the rear of the lower shielding layer 11, the lower core layer 13 is lowered to the same level as that of the lower shielding layer 11 through an inclined plane 13a. As shown in FIG. 14, the coil layer 14 is formed from on the inclined plane 13a to on the lower core layer 13 lying in the rear of the inclined plane 13a. Therefore, the insulating layer 17 is formed on the coil layer 14, being swollen from the surface S of the lower core layer 13 in the tip section by height t5, and the height t5 is smaller than the total thickness of the insulating layers 5 and 7 of the thin film magnetic head shown in FIG. 11. Accordingly, the thickness of a resist layer (not shown in the drawing; refer to numeral 10 in FIG. 12), which is formed on the lower core layer 13 around the tip, is not extremely increased, and in comparison with the thin film magnetic head shown in FIG. 11, a tip 15a of the upper core layer 15 can be easily formed in a predetermined shape.
In the thin film magnetic head shown in FIG. 14, however, the following problems may occur.
Generally, when a thin film magnetic head is formed, a plurality of thin film magnetic heads is simultaneously formed on a substrate 16 and by dividing into the individual thin film magnetic heads in the end, the thin film magnetic head shown in FIG. 14 can be obtained. That is, first, a plurality of lower shielding layers 11 is formed on the substrate 16, and a magnetoresistive element layer 12 is formed on each lower shielding layer 11 with an insulating layer (not shown in the drawing) therebetween. Next, a resist layer is applied onto a plurality of magnetoresistive element layers 12, and a track width Tw of the magnetoresistive element layer 12 is determined by exposure and development.
However, as described above, a plurality of magnetoresistive element layers 12 is placed on the substrate 16, and when the resist layer is, for example, spin-coated thereon, the surface onto which the resist layer is applied is not planar because the lower shielding layers 11 are selectively formed and there are steps between the lower shielding layers 11 and the substrate 16. Therefore, the resist layer is not formed at a uniform thickness, and a plurality of magnetoresistive element layers 12 formed on the substrate 16 cannot have a predetermined track width Tw.
In the thin film magnetic head shown in FIG. 14, the lower core layer 13 is provided with the inclined plane 13a, and the coil layer 14 is formed from on the inclined plane 13a to on the rear of the lower core layer 13. Since there is a difference in level on the inclined plane 13a on which the coil layer 14 is to be formed, the coil layer 14 is formed on the inclined plane 13a at a position that is raised upward in the drawing, and thus the thickness of the insulating layer 17 for covering the coil layer 14 must be increased. If the thickness of the insulating layer 17 is increased, it is difficult to form the tip 15a of the upper core layer 15 at a predetermined shape by frame plating, and narrowing of the track cannot be realized.